Conjugated linoleic acids (CLA) are naturally occurring geometric and positional isomers of linoleic acid, or octadecadienoic acid, produced naturally by microbes in the rumen of ruminant animals. Numerous therapeutic uses for CLA mixtures have been reported (see, e.g., U.S. Publ. No. 2005/0154059 and U.S. Pat. Nos. 6,395,782; 5,814,663; 5,760,082; and 5,585,400).
CLA contains two double bonds separated by a single bond in a cis, trans configuration that commonly occurs between the 8- and 13-carbon positions. The two most common isomers of CLA are trans-10, cis-12 and cis-9, trans-11. However, while most commercial synthetic CLA supplements contain an approximately equal amount of the trans-10, cis-12 and cis-9, trans-11 isomers (i.e., a 50:50 blend), the latter represents approximately 90-95% of the total CLA in rumenic food (i.e., dairy) products. Consequently, the cis-9, trans-11 isomer is commonly referred to as rumenic acid (RA).
Methods for making RA and rumenic acid-rich conjugated linoleic acid (RAR-CLA) have been reported (see, e.g., WO 2016/025312 and U.S. Pat. Nos. 8,614,074; 8,203,012; 6,897,327; 6,184,009; and 5,856,149). For instance, WO 2016/025312 describes a method in which a CLA-based triglyceride (Clarinol G-80, product of Stepan Lipid Nutrition) is selectively hydrolyzed using a lipase catalyst to give a mixture of unconverted triglycerides and a fatty acid mixture that is enriched in rumenic acid. The fatty acid mixture is separated by wiped-film evaporation from the less-volatile triglyceride component. The triglyceride component, which is enriched in the trans-10, cis-12 isomer, is also desirable as a therapeutic agent (see, e.g., U.S. Publ. No. 2013/0274336).
Rumenic acid has shown promise as an anti-inflammatory dietary supplement in humans. For example, Penedo et al. (J. Nutri. Biochem. 24 (2013) 2144) reported that 8 weeks of RA-enriched butter improved inflammatory markers in young, healthy men and women. Turpeinen et al. (Brit. J. Nutri. 100 (2008) 112) reported that 8 weeks of RA supplementation reduced the allergic responses mediated by inflammation in young men and women with birch pollen allergy. Sofi et al. (NMCD 20 (2010) 117) showed that 10 weeks of dietary supplementation with cheese naturally rich in RA (e.g., pecorino) reduced inflammation in middle-aged men and women. Therefore, despite limited applied studies in humans, existing evidence suggests that RA may have anti-inflammatory effects.
The mechanism of action for the anti-inflammatory effects of RA may be due to its actions as an agonist of peroxisome proliferator-activated receptor-γ (PPARγ). PPARγ is a ligand-activated transcription factor that regulates gene transcription. PPARγ is expressed in most tissues of the body and has important metabolic and inflammatory effects. Jaudszus et al. (Lipids Health Dis. 15 (2016) 1) demonstrated that RA reduced inflammatory responses in human epithelial cells via activation of PPARγ. Similarly, Y. Yu et al. (Biochim. Biophys. Acta, Mol. Cell Biol. Lipids 1581 (2002) 89) showed that RA activated PPARγ and served as an antioxidant in mouse macrophage cells. Therefore, investigators have suggested that RA may have therapeutic value in the management of conditions characterized by chronic inflammation such as atherosclerosis, asthma, inflammatory bowel disease, obesity, and aging.
Aging is associated with neurodegeneration, which describes a progressive deterioration and/or loss of neurons. Activation of PPARγ may reduce the risk of neurodegeneration. For example, based on studies in rodents, PPARγ activation has been shown to reduce cerebral ischemia/reperfusion injury (M. Collino et al., Eur. J. Pharmacol. 530 (2006) 70) and vascular aging (M. Modrick et al., Am. J. Physiol. Regul. Integr. Comp. Physiol. 302 (2012) R1184) by inhibiting oxidative stress and inflammation. M. Gama et al. (J. Neural Transm. 122 (2015) 1371) showed that dietary RA-enriched butter was associated with improved memory in rats. Thus, RA may have neuroprotective effects by way of anti-inflammatory, antioxidant, and vascular protection mediated by PPARγ activation (Y. Ulrich-Lai et al., Exp. Gerontol. 48 (2013) 671). Indeed, K. Yaffe et al. (Neurobiol. Aging 29 (2008) 78) demonstrated that older adults with a specific PPARγ polymorphism (e.g., Pro12Ala) had a decreased risk for age-related cognitive decline. Therefore, from an applied perspective, PPARγ activation by RA supplementation may improve cognitive function in older adults.
Compounds with PPARγ agonist activity (i.e., drugs such as glitizones and sartans) have been shown to improve cognitive function in older adults (R. Fogari et al., J. Hum. Hypertens. 17 (2003) 781; R. Fogari et al., Eur. J. Clin. Pharmacol. 59 (2004) 863; and M. Risner et al., Pharmacogenomics J. 6 (2006) 246) demonstrated that treatment with rosiglitazone improved attention and memory in patients with mild to moderate Alzheimer's disease. M. Gold and colleagues (Dement. Geriatr. Cogn. Disord. 30 (2010) 131), however, were unable to replicate these effects in a larger-scale, follow-up study. R. Fogari et al. (Eur. J. Clin. Pharmacol. 59 (2004) 863) demonstrated that valsartan improved word list memory and recall, but did not influence identification, verbal fluency, or word list recognition in hypertensive older adults. Similarly, R. Fogari et al. (J. Hum. Hypertens. 17 (2003) 781) demonstrated that losartan improved word list memory and recall, but not verbal fluency in hypertensive older adults.
Although many studies have examined PPARγ's cellular effects and demonstrated RA's activity as a PPARγ agonist, few studies have examined the effects of RA on applied, functional outcomes in humans, and no previous studies have investigated the effects of RAR-CLA on age-related decreases in cognitive function in humans.